Description

The class template signalN covers
several related classes signal0, signal1, signal2, etc.,
where the number suffix describes the number of function
parameters the signal and its connected slots will
take. Instead of enumerating all classes, a single pattern
signalN will be described, where N
represents the number of function parameters.

signalN
public
types

Slots of the extended_slot_type may be connected to the signal using the
connect_extended methods. The extended_slot_type
has an additional connection argument in its signature,
which gives slot functions access to their connection to the signal
invoking them.

typedefimplementation-detailslot_result_type;

This is the type returned when dereferencing the input iterators passed to the signal's
combiner. It is usually slot_function_type::result_type unless that
type is void, in which case slot_result_type is
unspecified.

signalN connection management

Connects the signal this to the incoming
slot. If the slot is inactive, i.e., any of the slots's tracked
objects have been destroyed, then the
call to connect is a no-op. If the second version of
connect is invoked, the
slot is associated with the given group. The at
parameter specifies where the slot should be connected:
at_front indicates that the slot will be
connected at the front of the list or group of slots and
at_back indicates that the slot will be
connected at the back of the list or group of
slots.

Returns:

A
connection
object that references the newly-created connection between
the signal and the slot; if the slot is inactive, returns a
disconnected connection.

Throws:

This routine meets the strong exception guarantee,
where any exception thrown will cause the slot to not be
connected to the signal.

Complexity:

Constant time when connecting a slot
without a group name or logarithmic in the number of groups
when connecting to a particular
group.

Notes:

It is unspecified whether connecting a slot while the
signal is calling will result in the slot being called
immediately.

The connect_extended methods work the same as the connect
methods, except they take slots of type extended_slot_type.
This is useful if a slot needs to access the connection between it and the
signal invoking it, for example if it wishes to disconnect or block the connection.

If the parameter is (convertible to) a
group name, any slots in the given group are
disconnected. Otherwise, any slots equal to the
given slot function
are disconnected.

Note, the slot_func
argument should not be an actual signals2::slot
object (which does not even support operator==), but rather
the functor you wrapped inside a signals2::slot
when you initially made the connection.

Throws:

Will not throw unless a user destructor or
equality operator == throws. If either throws,
not all slots may be disconnected.

Complexity:

If a group is given, O(lg g) + k where
g is the number of groups in the signal and k is the
number of slots in the group. Otherwise, linear in the
number of slots connected to the
signal.

If disconnecting a slot causes an exception to be
thrown, not all slots may be disconnected.

Complexity:

Linear in the number of slots known to the
signal.

Notes:

May be called at any time within the lifetime of the
signal, including during calls to the signal's slots.

boolempty() const;

Returns:

true if no slots
are connected to the signal, and
false otherwise.

Throws:

Will not throw.

Complexity:

Linear in the number of slots known to the
signal.

Rationale:

Slots can disconnect at any point in time,
including while those same slots are being invoked. It is
therefore possible that the implementation must search
through a list of disconnected slots to determine if any
slots are still connected.

std::size_tnum_slots() const;

Returns:

The number of slots connected to the signal

Throws:

Will not throw.

Complexity:

Linear in the number of slots known to the
signal.

Rationale:

Slots can disconnect at any point in time,
including while those same slots are being invoked. It is
therefore possible that the implementation must search
through a list of disconnected slots to determine how many
slots are still connected.

signalN invocation

Invokes the combiner with a
slot_call_iterator range
[first, last) corresponding to the sequence of calls to the
slots connected to signal
*this. Dereferencing an
iterator in this range causes a slot call with the given set
of parameters (a1, a2, ...,
aN), the result of which is returned from
the iterator dereference operation.

Returns:

The result returned by the combiner.

Throws:

If an exception is thrown by a slot call, or if the
combiner does not dereference any slot past some given slot,
all slots after that slot in the internal list of connected
slots will not be invoked.

Notes:

Only the slots associated with iterators that are
actually dereferenced will be invoked. Multiple dereferences
of the same iterator will not result in multiple slot
invocations, because the return value of the slot will be
cached.

The const version of
the function call operator will invoke the combiner as
const, whereas the
non-const version will
invoke the combiner as
non-const.

signalN combiner access

combiner_typecombiner() const;

Returns:

A copy of the stored combiner.

Throws:

Will not throw.

voidset_combiner(const combiner_type& combiner);

Effects:

Copies a new combiner into the signal for use with
future signal invocations.